N-phenyl-n&#39;-salicyloyl-phenylene diamines

ABSTRACT

CERTAIN SALICYLOYL DERIVATIVES SUCH AS N-PHENYL-N&#39;&#39;SALICYLOYL-P-PHENYLENEDIAMINE AND N-PHENYL-N&#39;&#39;-3-TERTIARYBUTYL SALICYLOYL-P-PHENYLENEDIAMINE AS ANTIOXIDANTS FOR OXIDIZABLE POLYMERS.

United States Patent 3,7 03,552 N-PHENYL-N'-SALICYLOYL-PHENYLENEDIAMINES US. Cl. 260-559 S 3 Claims ABSTRACT OF THE DISCLOSURE Certainsalicyloyl derivatives such as N-phenyl-N'-salicyloyl-p-phenylenediamine and N-phenyl-N-3-tertiarybutylsalicyloyl-p-phenylenediamine as antioxidants for oxidizable polymers.

This is a division of application Ser. No. 672,028, filed Oct. 2, 1967,now US. Pat. 3,558,552.

This invention relates to age resistors for oxidizable organicmaterials, their preparation and use in the stabilization of organicmaterials such as polymers, gasoline, oils, etc. which normally tend todeteriorate when exposed to normal atmospheric conditions and inparticular when exposed to sunlight and/or elevated temperature in thepresence of air or oxygen.

Polymers, including both natural rubber and synthetic polymers, haveproven to be some of the most difficult organic materials tosuccessfully stabilize against the deleterious effects of oxygen, ozoneand ultraviolet light. Both vulcanized and unvulcanized natural rubberand synthetic polymers are susceptible to the deleterious effects thatare found in normal atmospheric conditions and although many materialshave been suggested and used as polymer stabilizers, no completelysatisfactory material has been found that will completely protectpolymers under the widely different conditions to which they aresubjected. The search for new and better polymer stabilizers is,therefore, a problem which continues to command the attention of manyskilled investigators.

Phenolic and amine compounds have been among the more commonly usedclasses of compounds that have found wide scale acceptance as polymerstabilizers, but many of the phenolic antioxidants, although reasonablyeffective stabilizers for organic materials, tend to be susceptible tobeing too readily volatilized and, therefore, escape from the materialswhich they are intended to stabilize during the rather extended servicelife to which such materials are subjected.

It is, therefore, an object of this invention to provide a new class ofrelatively nonvolatile antioxidants and stabilizers for organiccompounds, in particular, polymers.

In accordance with the present invention it has been found that theforegoing objects can be accomplished by employing as stabilizers fororganic materials, particularly polymers, which are subject to thedeleterious effects of oxygen, ozone and sunlight, salicyloylderivatives of aromatic amines conforming to the following structuralformula:

wherein R is selected from the group consisting of hydrogen, alkylradicals containing 1 to 12 carbon atoms "ice and alkoxy radicalscontaining 1 to 12 carbon atoms and R is selected from the groupconsisting of wherein R and R are selected from the group eonsisting ofhydrogen and alkyl radicals containing 1 to 8 carbon atoms and R and Rare selected from the group consisting of hydrogen, alkyl radicalscontaining 1 to 8 carbon atoms and alkoxy radicals containing 1 to 6carbon atoms.

Examples of specific compounds conforming to the above recitedstructural formula are as follows:

N-salicyloyl-p-amino phenol N-salicyloyl-o-amino phenolN-salicyloyl-m-amino phenol N-salicyloyl-N-methyl-p-phenylenediamineN-salicyloyl-p-phenylenediamine N-4 ethyl salicyloyl-p-amino phenolN-4-ethoxy salicyloyl-p-amino phenolN-salicyloyl-N,N'-dimethyl-p-phenylenediamineN-salicyloyl-N',N'-diethyl-p-phenylenediamineN-salicyloyl-N',N'-dimethyl-o-phenylenediamineN-salicyloyl-N',N'-dimethyl-m-phenylenediamine N-4-methylsalicyloyl-N,N'-dimethyl-p-phenylenediamine N-4-ethoxysalicyloyl-N,N'-dimethyl-p-phenylenediamineN-phenyl-N-salicyloyl-p-phenylenediaminep-butylphenyl-N'salicyloyl-p-phenylenediamineN-o-tolyl-N'-salicyloyl-p-phenylenediamine N-phenyl-N-4-isopropylsalicyloyl-p phenylenediamine N-p-anisyl-N-salicyloyl-p-phenylenediamineThe preferred compounds within the scope of the present invention arethose conforming to the above recited structural formula wherein R is atertiary alkyl radical containing 4 to 12 carbon atoms and is located ina position ortho to the phenolic hydroxy group and wherein R is selectedfrom the group consisting of wherein R and R are selected from the groupconsisting of alkyl radicals containing 1 to 8 carbon atoms and R and Rare selected from the group consisting of hydrogen, alkyl radicalscontaining 1 to 4 carbon atoms and alkoxy radicals containing 1 to 2carbon atoms.

Examples of these preferred compounds are as follows:

N-phenyl-N'-3-tertiarybutyl salicyloyl-p-phenylenediamineN-phenyl-N'-3-tertiaryhexyl salicyloyl-p-phenylenediamineN-phenyl-N-3-tertiaryoctyl salicyloyl-o-phenylenediamineN-phenyl-N'-3-tertiaryamyl salicycloyl-m-phenylenediamineN-p-tolyl-N'-3-tertiarybutyl salicyloyl-p-phenylenediamineN-o-tolyl-N'-3-tertiaryhexyl salicyloyl-p-phenylenediamineN-2,4-dimethyl phenyl-N'-3-tertiarybutyl-p-phenylenediamineN,N-dimethyl-N'-3-tertiarybutyl salicyloyl-p-phenylenediamine 3N,N-diethyl-N'-3-tertiaryhexyl salicyloyl-p-phenylenediamineN,N-dibutyl-N'-3-tertiaryoctyl salicyloyl-p-phenylenediaminoN,N-dimethy1-N'-3-tertiarybutyl salicyloyl-o-phenylenediamineN,N-dipropyl-N-3-tertiaryamyl salicyloyl-m-phenylenediamine Mostpreferred are the compounds conforming to the above recited structuralformula wherein R is a radical of the structure:

wherein R and R are selected from the group consisting of hydrogen,alkyl radicals containing 1 to 4 carbon atoms and alkoxy radicalscontaining 1 to 2 carbon atoms.

Examples of the most preferred compounds are as follows:

N-phenyl-N'-salicyloyl-p-phenylenediamine N-phenyl-N'-3-tertiarybutylsalicyloyl-p-phenylenediamine N-p-tolyl-N'-salicyloyl-p-phenylenediamineN-p-tolyl-N-3-tertiaryamyl salicyloyl-p-phenylenediamine N-4-ethoxyphenyl-N'-salicyloyl-p-phenylenediamine N-4methoxyphenyl-N-3-tertiarybutyl salicyloyl-pphenylenediamineN-o-tolyl-N'-salicyloyl-p-phenylenediamine N-Z-methoxyphenyl-N-3-tertiaryhexyl salicyloyl-pphenylenediamine N-2,4-dimethylphenyl-N-salicyloyl-p-phenylene diamine N-2,4-dimethylphenyl-N'-3-tertiarybutyl salicyloyl-pphenylenediamine A particularlypreferred compound is N-phenyl-N- salicyloyl-p-phenylenediamine.

The salicyloyl derivatives of this invention may be made by reacting thephenyl or substittued phenyl salicylates with an aromatic primary amineat elevated temperatures (150 to 250 C.). After the reaction is completethe excess phenol is removed. The remaining reaction product may be usedas is or recrystallized from an appropriate solvent.

The compounds of this invention may be added to the polymer when it isin the form of a latex or solution or in solid form or when vulcanized.They are highly efficient and capable of being employed in relativelysmall amounts to effectively stabilize the polymers into which they areincorporated. The precise amount of these highly effective stabilizerswhich is to be employed will depend somewhat on the nature of thepolymer and the severity of the deteriorating conditions to which thepolymer is to be exposed. It has been found that an effectivestabilizing amount of the disclosed stabilizers will generally rangefrom 0.05 to 8.0 percent by weight based on the weight of the polymeralthough in most rubbery polymers it is commonly preferred to use from0.5 to 2.0 percent of the rubber. In the stabilization of relativelyunsaturated polymers such as polyethylene levels of 0.001 part and lowerwill afford protection.

The polymers that may be conveniently protected by the phenoliccompounds in accordance with this invention are vulcanized andunvulcanized oxidizable polymers such as natural rubber and thosesynthetic oxidizable polymers which are normally susceptible todeterioration by sunlight and atmospheric oxygen such as the syntheticpolymers and copolymers prepared from conjugated dienes as well as thesynthetic polymers and copolymers prepared from monoolefiins.Representative examples of the synthetic olymers used in the ractice ofthis invention are polychloroprene; homopolymers of a conjugated 1,3-diene such as isoprene and butadiene and in particular, polyisoprenesand polybutadienes having essentially all of their segmaric unitscombined in a cis-1,4 structure; copolymers of a conjugated 1,3-dienesuch as isoprene and butadiene with up to 50 percent by weight of atleast one copolymerizable monomer such as styrene, acrylonitrile,unsaturated carboxylic acids, including acrylic, methacrylic, fumaricand itaconic acid; butyl rubber, which is a polymerization product of amajor proportion of a monoolefin and a minor proportion of a multiolefinsuch as butadiene or isoprene; and polymers and copolymers ofmonoolefins containing little or no unsaturation, such as polyethylene,polypropylene, ethylene propylene copolymers and terpolymers ofethylene, propylene and a nonconjugated diene.

The practice of this invention is found particularly beneficial whenapplied to the stabiilzation of natural rubber and homopolymers of aconjugated 1,3-diene such as isoprene and butadiene and copolymers ofsaid diene with up to 50 percent by weight of at least onecopolymerizable monomer such as styrene and acrylonitrile.

The following Examples 1 to 3 illustrate the preparation of materialsaccording to the practice of the present invention but are not intendedto so limit the scope of the invention.

EXAMPLE 1 Ninety-two grams of p-aminodiphenylamine and grams of phenylsalicylate were heated between and C. for 7 /2 hours. The reaction masswas then heated to 185 C. at 25 mm. of Hg to remove 45.5 grams of phenolthat had formed. The residue, weighing 132 grams, melted between 151 and154 C. This represents a yield of about 87 percent.

The product, N phenyl N salicyloyl-p-phenylenediamine, wasrecrystallized twice from hot toluene and found to contain 9.18 percentnitrogen compared to a theoretical value of 9.21 percent.

EXAMPLE 2 Eighty-two grams of N,N diethyl-p-phenylenediamine and 125grams of phenyl salicylate were heated between 175 and 180 C. for sixhours. They were then heated under vacuo to remove phenol. The weight ofproduct obtained was 151.0 grams, a quantitative yield. The product wasessentially N-salicyloyl-N,N-diethyl-p-phenylenediamine.

EXAMPLE 3 One hundred and nine grams of p-amino phenol and 240 grams ofphenyl salicylate were heated for five hours at C. followed by heatingunder vacuo to remove the phenol formed. The residue was then extractedwith toluene to remove excess phenyl salicylate. Weight of final productwas 163.0 grams. The product had a melting point of 172 C. to 173.5 C.and a nitrogen value of 6.02 percent compared to a theoretical nitrogencontact for N- salicyloyl-p-amino phenol of 6.1 percent.

EXAMPLE 4 The antioxidant properties of the products of Examples l, 2and 3 were measured by oxygen absorption tests by dissolving in benzeneportions of an SBR polymer (1006) containing 1.00 part per 100 parts ofrubbery polymer of the products of Examples 1, 2 and 3. The cements soformed were poured onto aluminum foil so as to form a thin film anddried to obtain the weight of rubber for each sample. Thereafter thefoil with the adhering rubber strip was placed in an oxygen absorptionapparatus. The amount of oxygen absorbed in a particular interval oftime was determined and recorded in the following Table I. This testingprocedure is described in further detail in Industrial and EngineeringChemistry, 43, p. 456 (1951) and Industrial and Engineering Chemistry,45, p. 392 (1953).

TABLE I Oxygen absorption hours/per- Experi cent oxygen ment Antioxidantabsorbed A Commercial phenolic antioxidant 1 403/10 B N-phenylN -salioyloyl-p-phenylenediamine. 668/038 N-salieylyl-p-amino phenol 79/10 DCommercial phenolic antioxidant l 212/1.0 EN,N-diethyl-N-salieyloyl-p-phenylenediamine 63/10 1 An alkylated phenol.

An unstabilized SBR 1006 would normally reach a value of 1.0 percent in2 to 24 hours, most normally in about four hours. Experiments B and Cwere run separately from Experiment E. Therefore the control run withExperiments B and C (Experiment A) and the control run with Experiment E(Experiment D) have been listed. As

the above data demonstrate, all of the stabilizers wittu'n the scope ofthe present invention (Experiments B, C and E) aflforded the SBR polymerprotection against oxygen degradation.N-phenyl-N-salicyloyl-p-phenylenediamine (Experiment B) was greatlysuperior to the other stabilizers tested.

EXAMPLE The products of Examples 1, 2 and 3 were also used to stabilizean extracted pale crepe natural rubber. One part of each product wasadded to a portion of the natural rubber as part of the followingformulation:

Ingredients: Parts Extracted pale crepe 100 ZnO 5 Sulfur 3 Hexamethylenetetramine l Stearic acid 1.5

Antioxidant l TABLE II Tensile (p.s.i.) Percent Experitnsile mentAntioxidant Unaged aged retention F None 2,100 0 0 GN-phenyl-N-salieyloyl-p- 1,850 1,930 104.2

phenylenediamine (Example IEI N-salieyloyl-p-amino phenol 2, 190 490 22.2

(Example 2). I N,N-diethyl-N-salicyloyl-p- 1,770 1,900 107.2

ghenylenediamine (Example The above tensile retention data reveal thatall of the stabilizers within the scope of the present invention(Experiments G, H and I) afforded protection to the natural rubber. TheN-phenyl-N'-salicyloyl-p-phenylenediamine and N,N diethylN-salicyloyl-p-phenylenediamine were particularly effective, allowing noreduction in tensile whatsoever on aging.

In addition to protecting polymers against degradation by oxygen, thesalicyloyls of the present invention also show absorption of ultravioletlight in the region most detrimental to polymers. Materials which absorbultraviolet light in this region are known in general to be inhibitorsof polymeric degradation due to ultraviolet light. These salicyloyls arealso effective as metal deactivators in systems where the presence ofmetal accelerates the deterioration of polymers. In addition, thesecomponnds are less discoloring in a polymeric environment than manyamine age resisters.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in this art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

What I claim is:

1. A compound conforming to the following structural formula:

on R4 N-phenyl-N'-salicyloyl-pphenylenediamine,N-p-tolyl-N'-salicyloyl-p-phenylenediamine,N-4-methoxyphenyl-N-salicyloyl-p-phenylenediamine,N-4-methoxyphenyl-N-3-tert.butyl salicyloyl-p-phenylenediamine,N-O-tolyl-N-salicyloy1-p-phenylenediamine,N-2,4-dimethylphenyl-N'-salicyloyl-p-phenylenediamine.

References Cited UNITED STATES PATENTS 1/1968 Huey et a1 260559 S OTHERREFERENCES Charlier et al.: Arzneimittel-Forsch, vol. 9, pp. 210-12(1959).

Chemical Abstracts, vol. 63, col. 8253-64 (1965) (Davidova article VanAllan, J. Am. Chem. Soc., vol. 69, pp. 2913-14 (1967)).

HENRY R. JILES, Primary Examiner H. I. MOATZ, Assistant Examiner US. Cl.X.R.

' 133g? UNITED STATES PATENT OFCE CERTIFICATE OF CORRECTION Patent No. R3,703,552 I V Dated November 21, 1972 mem g -Ronald B. Spacht It iscertified that error appears in the above-1dentified patent and thatsaid Letters Patent are hereby corrected as shown below:

The patent should indicate that Ronald B. ,Spacht is "1 an assignor to--The Goodyear Tire & Rubber Company,

' Akron, Ohio-n Column 3-, line r, "diamino" .should read "die mine",

Column 3, line 62, after "percent" the following was omitted, "by weightbased on the weight".

Signed and sealed this 17th day of April 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. V i ROBERT GOTTSCHALK Attesting OfficerCommissioner of Patents

